The invention relates to a safety device for systems using gas and having a gas shut-off element that is inserted into the gas connecting line and responds to an incorrect escape of gas in the immediate surrounding area. Devices of this type are used for monitoring local pipeline networks for leaking connecting points and for leaks caused by mechanical effects, corrosion or electrolytic destruction, in order to be able to rectify this damage without delay.
In view of the above, the invention is based on the object of using such a safety device to automatically actuate a gas shut-off element inserted into the connecting pipeline at a suitable point in the event of a gas escape caused by a defect.
In order to achieve this object, the invention forms a safety device for systems using gas according to patent claim 1 to the effect that a gas shut-off element connected into the gas connecting line has a pneumatic operating cylinder arranged on the outside, whose actuating piston is coupled mechanically to the closure part of the gas shut-off element. This actuating piston is held in a position corresponding to the open position of the gas shut-off element by the pressure of a liquid-gas cartridge acting on the operating cylinder and against the force of a closing spring. At the same time, a vent valve which is supplied with the operating cylinder and which is controlled electronically by a gas sensor responding to an incorrect escape of gas in the monitoring area, relieves the pressure on the actuating piston and, as a result of the latter, changes the gas shut-off element from its open position into the closed position.
Expedient configurations and advantageous developments of the invention can be seen from the subsequent subclaims 2 to 11.
According to the features of claim 2, the gas shut-off element inserted into the connecting line is constituted as a pipeline switch in the form of a cock, a flap, a slide or a valve, whose respective actuation is matched to the defined linear movement of the actuating piston within the pneumatic operating cylinder by means of a mechanical gear mechanism.
The vent valve for the operating cylinder and for the liquid-gas cartridge is, according to the features of claim 1, a valve which can initially be set manually into its blocking position against the prevailing line pressure in the monitoring system and which is held in this position by an electromagnet functioning on the quiescent current principle. Accordingly, switching it off by means of the gas sensor used in the respective monitoring area, together with the opening of the vent valve, has the effect of relieving the actuating piston within the operating cylinder in the effect on the gas shut-off element coupled to the piston.
According to the features of claim 4, a combined switching-on mechanism is provided for the replacement of the discharged liquid-gas cartridge, which is necessary for the first time the safety device is commissioned and, after that, is necessary in relation to the repeated commissioning of the safety device following a fault. Said mechanism is, for example, constructed as an actuating handle which is mounted like a lever and such that it can be pivoted on the housing designed to accommodate the various functional elements of the safety device. Using said actuating handle, one after another, firstly the power supply for the monitoring circuit comprising the gas sensor and retaining magnet can be switched on, then the vent valve operated by the energized retaining magnet can be moved into its closed position, and finally the liquid-gas cartridge moving the operating cylinder pneumatically into the corresponding open position of the actual gas shut-off element can be activated by being pressed in a sealing manner into the connecting safeguard present on its mount. Here, any operating errors and non-permitted manipulations, technical defects in individual function elements or else aging phenomena always have the effect of blocking the threatened gas supply and therefore ensure the unconditional intrinsic safety of the overall device.
In order to trigger the safety device in the event of a fault, the gas sensor that reacts to the presence of gas in the monitoring area is equipped, according to the features of claim 5, with an electric changeover contact, by means of which the power supply to the retaining magnet for the vent valve is interrupted in an explosion-proof manner and, instead, an optical or acoustic warning signal is switched on. In this way, the vent valve which relieves the operating cylinder of the pressure from the liquid-gas cartridge automatically effects the safe closing operation of the gas shut-off element under spring force.
In this safety device, a shut-off flap within the gas connecting line is operated, for example, by means of an operating cylinder which is fitted to the outside of the relevant pipeline fitting, to which end the engagement of the necessary coupling linkage on the side of the gas connecting line makes sealing measures necessary, which have to be implemented carefully and be maintained-at time intervals. On the other hand, if a ball cock is used as the gas shut-off element, the outlay on apparatus for converting the linear movement of the actuating piston into a rotational movement, which is loaded by the seal, of the closure part on the side of the cock is likewise complicated, and also overcoming the breaking forces which may occur on the sealing surfaces following a relatively long residence time in the operating state.
In order to avoid such sealing problems and to reduce the effort necessary for actuating a gas shut-off element, according to an advantageous development according to claim 6, the invention forms the same as a through valve which is arranged within the pipeline fitting and, on its own, is itself spring-loaded to close. Furthermore, the valve is held by a pivotable coupling element such that it can be displaced by means of a bellows which, fitted from the outside, engages in the fitting, the bellows, in the operating state, being held in the expanded position by the pressure of the filling of a liquid-gas cartridge and against the restoring force of its own helical compression spring.
The bellows operates as pneumatic operating cylinder and actuating piston of the device at the same time.
In this way, any sealing measures for the gas shut-off element that has to be actuated in the event of a hazard are dispensed with, because of the servomechanisms which are now incorporated directly into the gas-tight pipeline fitting area.
According to the features of claim 7, the through valve in this safety device has a valve disk which can be displaced coaxially and is held by its valve stem on the inner wall of the pipeline fitting by means of radial struts which permit flow. In addition, the closing spring which presses the valve disk against a seating face of the through valve, which is incorporated into the inner wall of the fitting, is supported on the same radial struts. The opening of the valve therefore takes place against the force of this closing spring, which has the effect of blocking the gas supply in every case and with safety in the event of a failure or fault in the actuating torque.
In this case, the bellows that functions as the pneumatic actuator for the valve actuation, according to the features of claim 8, is as such arranged within a pipe connecting piece inserted tightly from the outside into a lateral wall opening in the pipeline fitting. To this end, the free actuating end of the bellows, according to the features of claim 9, is engaged over loosely by a peened-over edge angled inward of a sleeve-like support element which, at its other end, has a peened-over edge angled outward, on which the restoring spring acting against a shoulder on the inner wall of the inserted connecting piece is supported, in order to guide the pneumatically depressurized bellows back into its compressed starting position.
According to the features of claim 10, a two-armed coupling element which can be loaded by the actuating end of the bellows is pivotably mounted at the opening of the inserted connecting piece which reaches into the pipeline fitting, in order to act with its longer lever arm, via a connecting pin guided concentrically within the fitting, on the adjustable valve disk of the through valve. In this way, the respective valve actuation takes place, so to speak in a space which is tightly closed and filled with gas.
In addition, according to the features of claim 11, a solenoid valve which can be triggered in a defined manner is inserted into the capillary tube connection between the bellows serving as the actuator for the through valve and the liquid-gas cartridge which can be inserted interchangeably into the overall device as an energy store, it being possible for said solenoid valve to vent the relevant operative connection and therefore to block the through valve for the gas supply safely.
In this case, this vent valve is preferably triggered in an explosion-proof manner in an electronic way by one or more gas sensors which, in order to monitor the gas concentration present in the environment, are in each case arranged in a potential hazardous area.
Claims 12 and 25 describe the invention in terms of a pneumatic actuator that converts a changing pressure of a pressure source into a mechanical movement of an actuating element. Two possible realisations of such a pneumatic actuator are the operating cylinder/actuating piston and the bellows explained above. Therefore, the above explanations apply analogously to claims 12 to 25, too.